SECTION 23 31 00
HVAC DUCTS AND CASINGS
PART 1 - GENERAL
1.1 DESCRIPTION
A. Ductwork and accessories for HVAC including the following:
1. Supply air, return air, outside air, exhaust, make-up air, and relief systems.
2. Exhaust duct with HEPA filters for Negative Pressure Isolation Room, mail room, and
otherwise as indicated on the Drawings.
B. Definitions:
1. SMACNA Standards as used in this specification means the HVAC Duct Construction
Standards, Metal and Flexible.
2. Seal or Sealing: Use of liquid or mastic sealant, with or without compatible tape overlay, or
gasketing of flanged joints, to keep air leakage at duct joints, seams and connections to an
acceptable minimum.
3. Duct Pressure Classification: SMACNA HVAC Duct Construction Standards, Metal and
Flexible.
4. Exposed Duct: Exposed to view in a finished room, exposed to weather.
1.2 RELATED WORK
A. Fire Stopping Material: Section 07 84 00, FIRESTOPPING.
B. Outdoor and Exhaust Louvers: Section 08 90 00, LOUVERS and VENTS.
C. Seismic Reinforcing: Section 13 05 41, SEISMIC RESTRAINT REQUIREMENTS FOR NONSTRUCTURAL COMPONENTS.
D. General Mechanical Requirements: Section 23 05 11, COMMON WORK RESULTS FOR HVAC
and STEAM GENERATION.
E. Noise Level Requirements: Section 23 05 41, NOISE AND VIBRATION CONTROL FOR HVAC
PIPING and EQUIPMENT.
F. Duct Insulation: Section 23 07 11, HVAC, PLUMBING, and BOILER PLANT INSULATION
G. Plumbing Connections: Section 22 11 00, FACILITY WATER DISTRIBUTION
H. Air Flow Control Valves and Terminal Units: Section 23 36 00, AIR TERMINAL UNITS.
I.
Duct Mounted Coils: Section 23 82 16, AIR COILS.
J.
Return Air and Exhaust Air Fans: Section 23 34 00, HVAC FANS.
K. Air Filters and Filters' Efficiencies: Section 23 40 00, HVAC AIR CLEANING DEVICES.
L. Duct Mounted Instrumentation: Section 23 09 23, DIRECT-DIGITAL CONTROL SYSTEM FOR
HVAC.
M. Testing and Balancing of Air Flows: Section 23 05 93, TESTING, ADJUSTING, and BALANCING
FOR HVAC.
N. Smoke Detectors: Section 28 31 00, FIRE DETECTION and ALARM.
1.3 QUALITY ASSURANCE
A. Refer to article, QUALITY ASSURANCE, in Section 23 05 11, COMMON WORK RESULTS FOR
HVAC and STEAM GENERATION.
B. Fire Safety Code: Comply with NFPA 90A.
C. Duct System Construction and Installation: Referenced SMACNA Standards are the minimum
acceptable quality.
D. Duct Sealing, Air Leakage Criteria, and Air Leakage Tests: Ducts shall be sealed as per duct
sealing requirements of SMACNA HVAC Air Duct Leakage Test Manual for duct pressure classes
shown on the drawings.
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E. Duct accessories exposed to the air stream, such as dampers of all types (except smoke
dampers) and access openings, shall be of the same material as the duct or provide at least the
same level of corrosion resistance.
1.4 SUBMITTALS
A. Submit in accordance with Section 01 33 23, SHOP DRAWINGS, PRODUCT DATA, and
SAMPLES.
B. Manufacturer's Literature and Data:
1. Rectangular ducts:
a. Schedules of duct systems, materials and selected SMACNA construction alternatives for
joints, sealing, gage and reinforcement.
b. Duct liner.
c.
Sealants and gaskets.
d. Access doors.
2. Round and flat oval duct construction details:
a. Manufacturer's details for duct fittings.
b. Duct liner.
c.
Sealants and gaskets.
d. Access sections.
e. Installation instructions.
3. Volume dampers, back draft dampers.
4. Upper hanger attachments.
5. Fire dampers, fire doors, and smoke dampers with installation instructions.
6. Sound attenuators, including pressure drop and acoustic performance.
7. Flexible ducts and clamps, with manufacturer's installation instructions.
8. Flexible connections.
9. Instrument test fittings.
10 Details and design analysis of alternate or optional duct systems.
11 COMMON WORK RESULTS FOR HVAC and STEAM GENERATION.
C. Coordination Drawings: Refer to article, SUBMITTALS, in Section 23 05 11 – Common Work
Results for HVAC and Steam Generation.
1.5 APPLICABLE PUBLICATIONS
A. The publications listed below form a part of this specification to the extent referenced. The
publications are referenced in the text by the basic designation only.
B. American Society of Civil Engineers (ASCE):
ASCE7-05 .................................. Minimum Design Loads for Buildings and Other Structures
C. American Society for Testing and Materials (ASTM):
A167-99(2009) ........................... Standard Specification for Stainless and Heat-Resisting
Chromium-Nickel Steel Plate, Sheet, and Strip
A653-09 ...................................... Standard Specification for Steel Sheet, Zinc-Coated
(Galvanized) or Zinc-Iron Alloy coated (Galvannealed) by the
Hot-Dip process
A1011-09a .................................. Standard Specification for Steel, Sheet and Strip, Hot rolled,
Carbon, structural, High-Strength Low-Alloy, High Strength LowAlloy with Improved Formability, and Ultra-High Strength
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B209-07 ...................................... Standard Specification for Aluminum and Aluminum-Alloy Sheet
and Plate
C1071-05e1 ............................... Standard Specification for Fibrous Glass Duct Lining Insulation
(Thermal and Sound Absorbing Material)
E84-09a ...................................... Standard Test Method for Surface Burning Characteristics of
Building Materials
D. National Fire Protection Association (NFPA):
90A-09 ........................................ Standard for the Installation of Air Conditioning and Ventilating
Systems
96-08 .......................................... Standard for Ventilation Control and Fire Protection of
Commercial Cooking Operations
E. Sheet Metal and Air Conditioning Contractors National Association (SMACNA):
2nd Edition – 2005 ..................... HVAC Duct Construction Standards, Metal and
Flexible
1st Edition - 1985 ....................... HVAC Air Duct Leakage Test Manual
6th Edition – 2003 ...................... Fibrous Glass Duct Construction Standards
F. Underwriters Laboratories, Inc. (UL):
181-08 ........................................ Factory-Made Air Ducts and Air Connectors
555-06 ....................................... Standard for Fire Dampers
555S-06 ..................................... Standard for Smoke Dampers
PART 2 - PRODUCTS
2.1 DUCT MATERIALS AND SEALANTS
A. General: Except for systems specified otherwise, construct ducts, casings, and accessories of
galvanized sheet steel, ASTM A653, coating G90; or, aluminum sheet, ASTM B209, alloy 1100,
3003 or 5052.
B. Specified Corrosion Resistant Systems: Stainless steel sheet, ASTM A167, Class 302 or 304,
Condition A (annealed) Finish No. 4 for exposed ducts and Finish No. 2B for concealed duct or
ducts located in mechanical rooms.
C. Joint Sealing: Refer to SMACNA HVAC Duct Construction Standards, paragraph S1.9.
1. Sealant: Elastomeric compound, gun or brush grade, maximum 25 flame spread and 50
smoke developed (dry state) compounded specifically for sealing ductwork as recommended
by the manufacturer. Generally provide liquid sealant, with or without compatible tape, for low
clearance slip joints and heavy, permanently elastic, mastic type where clearances are larger.
Oil base caulking and glazing compounds are not acceptable because they do not retain
elasticity and bond.
2. Tape: Use only tape specifically designated by the sealant manufacturer and apply only over
wet sealant. Pressure sensitive tape shall not be used on bare metal or on dry sealant.
3. Gaskets in Flanged Joints: Soft neoprene.
D. Approved factory made joints may be used.
2.2 DUCT CONSTRUCTION AND INSTALLATION
A. Regardless of the pressure classifications outlined in the SMACNA Standards, fabricate and seal
the ductwork in accordance with the following pressure classifications:
B. Duct Pressure Classification:
0 to 50 mm (2 inch)
> 50 mm to 75 mm (2 inch to 3 inch)
> 75 mm to 100 mm (3 inch to 4 inch)
Show pressure classifications on the floor plans.
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C. Seal Class: All ductwork shall receive Class A Seal
D. Duct for Negative Pressure Up to 750 Pa (3 inch W.G.): Provide for exhaust duct between HEPA
filters and exhaust fan inlet including systems for Autopsy Suite exhaust.
1. Round Duct: Galvanized steel, spiral lock seam construction with standard slip joints.
2. Rectangular Duct: Galvanized steel, minimum 1.0 mm (20 gage), Pittsburgh lock seam,
companion angle joints 32 mm by 3.2 mm (1-1/4 by 1/8 inch) minimum at not more than 2.4
m (8 feet) spacing. Approved pre-manufactured joints are acceptable in lieu of companion
angles.
E. Round and Flat Oval Ducts: Furnish duct and fittings made by the same manufacturer to insure
good fit of slip joints. When submitted and approved in advance, round and flat oval duct, with
size converted on the basis of equal pressure drop, may be furnished in lieu of rectangular duct
design shown on the drawings.
1. Elbows: Diameters 80 through 200 mm (3 through 8 inches) shall be two sections die
stamped, all others shall be gored construction, maximum 18 degree angle, with all seams
continuously welded or standing seam. Coat galvanized areas of fittings damaged by welding
with corrosion resistant aluminum paint or galvanized repair compound.
2. Provide bell mouth, conical tees or taps, laterals, reducers, and other low loss fittings as
shown in SMACNA HVAC Duct Construction Standards.
3. Ribbed Duct Option: Lighter gage round/oval duct and fittings may be furnished provided
certified tests indicating that the rigidity and performance is equivalent to SMACNA standard
gage ducts are submitted.
a. Ducts: Manufacturer's published standard gage, G90 coating, spiral lock seam
construction with an intermediate standing rib.
b. Fittings: May be manufacturer's standard as shown in published catalogs, fabricated by
spot welding and bonding with neoprene base cement or machine formed seam in lieu of
continuous welded seams.
4. Provide flat side reinforcement of oval ducts as recommended by the manufacturer and
SMACNA HVAC Duct Construction Standard S3.13. Because of high pressure loss, do not
use internal tie-rod reinforcement unless approved by the Resident Engineer.
F. Casings and Plenums: Construct in accordance with SMACNA HVAC Duct Construction
Standards Section 6, including curbs, access doors, pipe penetrations, eliminators and drain
pans. Access doors shall be hollow metal, insulated, with latches and door pulls, 500 mm (20
inches) wide by 1200 - 1350 mm (48 - 54 inches) high. Provide view port in the doors where
shown. Provide drain for outside air louver plenum. Outside air plenum shall have exterior
insulation. Drain piping shall be routed to the nearest floor drain.
G. Volume Dampers: Single blade or opposed blade, multi-louver type as detailed in SMACNA
Standards. Refer to SMACNA Detail Figure 2-12 for Single Blade and Figure 2.13 for Multi-blade
Volume Dampers.
H. Duct Hangers and Supports: Refer to SMACNA Standards Section IV. Avoid use of trapeze
hangers for round duct.
2.3 DUCT LINER (WHERE INDICATED ON DRAWINGS)
A. Duct sizes shown on drawings for lined duct are clear opening inside lining.
B. Duct liner is only permitted to be used for return, relief and general exhaust ducts. Duct liner is
not permitted for outside air ducts, supply air ducts or any other positive pressure ductwork
(provide exterior insulation only).
C. Rectangular Duct or Casing Liner: ASTM C1071, Type I (flexible), or Type II (board), 25 mm (one
inch) minimum thickness, applied with mechanical fasteners and 100 percent coverage of
adhesive in conformance with SMACNA, Duct Liner Application Standard.
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D. Round and Oval Duct Liner: Factory fabricated double-walled with 25 mm (one inch) thick sound
insulation and inner perforated galvanized metal liner. Construction shall comply with flame and
smoke rating required by NFPA 90A. Metal liner shall be 1.0 to 0.60 mm (20 to 24 gage) having
perforations not exceeding 2.4 mm (3/32 inch) diameter and approximately 22 percent free area.
Metal liner for fittings need not be perforated. Assemblies shall be complete with continuous
sheet Mylar liner, 2 mil thickness, between the perforated liner and the insulation to prevent
erosion of the insulation. Provide liner couplings/spacer for metal liner. At the end of insulated
sections, provide insulation end fittings to reduce outer shell to liner size. Provide liner
spacing/concentricity leaving airway unobstructed.
2.4 DUCT ACCESS DOORS, PANELS AND SECTIONS
A. Provide access doors, sized and located for maintenance work, upstream, in the following
locations:
1. Each duct mounted coil and humidifier.
2. Each fire damper (for link service), smoke damper and automatic control damper.
3. Each duct mounted smoke detector.
4. For cleaning operating room supply air duct and kitchen hood exhaust duct, locate access
doors at 6 m (20 feet) intervals and at each change in duct direction.
B. Openings shall be as large as feasible in small ducts, 300 mm by 300 mm (12 inch by 12 inch)
minimum where possible. Access sections in insulated ducts shall be double-wall, insulated.
Transparent shatterproof covers are preferred for uninsulated ducts.
1. For rectangular ducts: Refer to SMACNA HVAC Duct Construction Standards (Figure 2-12).
2. For round and flat oval duct: Refer to SMACNA HVAC duct Construction Standards (Figure
2-11).
2.5 FIRE DAMPERS
A. Galvanized steel, interlocking blade type, UL listing and label, 1-1/2 hour rating, 70 degrees C
(160 degrees F) fusible line, 100 percent free opening with no part of the blade stack or damper
frame in the air stream.
B. Fire dampers in wet air exhaust shall be of stainless steel construction, all others may be
galvanized steel.
C. Minimum requirements for fire dampers:
1. The damper frame may be of design and length as to function as the mounting sleeve, thus
eliminating the need for a separate sleeve, as allowed by UL 555. Otherwise provide sleeves
and mounting angles, minimum 1.9 mm (14 gage), required to provide installation equivalent
to the damper manufacturer's UL test installation.
2. Submit manufacturer's installation instructions conforming to UL rating test.
2.6 SMOKE DAMPERS
A. Maximum air velocity, through free area of open damper, and pressure loss: Low pressure and
medium pressure duct (supply, return, exhaust, outside air): 450 m/min (1500 fpm). Maximum
static pressure loss: 32 Pa (0.13 inch W.G.).
B. Maximum air leakage, closed damper: 0.32 cubic meters /min/square meter (4.0 CFM per square
foot) at 750 Pa (3 inch W.G.) differential pressure.
C. Minimum requirements for dampers:
1. Shall comply with requirements of Table 6-1 of UL 555S, except for the Fire Endurance and
Hose Stream Test.
2. Frame: Galvanized steel channel with side, top and bottom stops or seals.
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3. Blades: Galvanized steel, parallel type preferably, 300 mm (12 inch) maximum width, edges
sealed with neoprene, rubber or felt, if required to meet minimum leakage. Airfoil
(streamlined) type for minimum noise generation and pressure drop are preferred for duct
mounted dampers.
4. Shafts: Galvanized steel.
5. Bearings: Nylon, bronze sleeve or ball type.
6. Hardware: Zinc plated.
7. Operation: Automatic open/close. No smoke damper that requires manual reset or link
replacement after actuation is acceptable. See drawings for required control operation.
D. Motor operator (actuator): Provide pneumatic or electric as required by the automatic control
system, externally mounted on stand-offs to allow complete insulation coverage.
2.7 COMBINATION FIRE AND SMOKE DAMPERS
Combination fire and smoke dampers: Multi-blade type units meeting all requirements of both fire
dampers and smoke dampers shall be used where shown and may be used at the Contractor's
option where applicable.
2.8 FIRE DOORS
Galvanized steel, interlocking blade type, UL listing and label, 71 degrees C (160 degrees F)
fusible link, 3 hour rating and approved for openings in Class A fire walls with rating up to 4 hours,
100 percent free opening with no part of the blade stack or damper frame in the air stream.
2.9 FLEXIBLE AIR DUCT
A. General: Factory fabricated, complying with NFPA 90A for connectors not passing through floors
of buildings. Flexible ducts shall not penetrate any fire or smoke barrier which is required to have
a fire resistance rating of one hour or more. Flexible duct length shall not exceed 1.5 m (5 feet).
Provide insulated acoustical air duct connectors in supply air duct systems and elsewhere as
shown.
B. Flexible ducts shall be listed by Underwriters Laboratories, Inc., complying with UL 181. Ducts
larger than 200 mm (8 inches) in diameter shall be Class 1. Ducts 200 mm (8 inches) in diameter
and smaller may be Class 1 or Class 2.
C. Insulated Flexible Air Duct: Factory made including mineral fiber insulation with maximum C
factor of 0.25 at 24 degrees C (75 degrees F) mean temperature, encased with a low permeability
moisture barrier outer jacket, having a puncture resistance of not less than 50 Beach Units.
Acoustic insertion loss shall not be less than 3 dB per 300 mm (foot) of straight duct, at 500 Hz,
based on 150 mm (6 inch) duct, of 750 m/min (2500 fpm).
D. Application Criteria:
1. Temperature range: -18 to 93 degrees C (0 to 200 degrees F) internal.
2. Maximum working velocity: 1200 m/min (4000 feet per minute).
3. Minimum working pressure, inches of water gage: 2500 Pa (10 inches) positive, 500 Pa (2
inches) negative.
E. Duct Clamps: 100 percent nylon strap, 80 kg (175 pounds) minimum loop tensile strength
manufactured for this purpose or stainless steel strap with cadmium plated worm gear tightening
device. Apply clamps with sealant and as approved for UL 181, Class 1 installation.
2.10 FLEXIBLE DUCT CONNECTIONS
Where duct connections are made to fans, air terminal units, and air handling units, install a
non-combustible flexible connection of 822 g (29 ounce) neoprene coated fiberglass fabric
approximately 150 mm (6 inches) wide. For connections exposed to sun and weather provide
hypalon coating in lieu of neoprene. Burning characteristics shall conform to NFPA 90A. Securely
fasten flexible connections to round ducts with stainless steel or zinc-coated iron draw bands with
worm gear fastener. For rectangular connections, crimp fabric to sheet metal and fasten sheet
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metal to ducts by screws 50 mm (2 inches) on center. Fabric shall not be stressed other than by
air pressure. Allow at least 25 mm (one inch) slack to insure that no vibration is transmitted.
2.11 SOUND ATTENUATING UNITS
A. Casing, not less than 1.0 mm (20 gage) galvanized sheet steel, or 1.3 mm (18 gage) aluminum
fitted with suitable flanges to make clean airtight connections to ductwork. Sound-absorbent
material faced with glass fiber cloth and covered with not less than 0,6 mm (24 gage) or heavier
galvanized perforated sheet steel, or 0.85 mm (22 gage) or heavier perforated aluminum.
Perforations shall not exceed 4 mm (5/32-inch) diameter, approximately 25 percent free area.
Sound absorbent material shall be long glass fiber acoustic blanket meeting requirements of
NFPA 90A.
B. Entire unit shall be completely air tight and free of vibration and buckling at internal static
pressures up to 2000 Pa (8 inches W.G.) at operating velocities.
C. Pressure drop through each unit: Not to exceed indicated value at design air quantities indicated.
D. Submit complete independent laboratory test data showing pressure drop and acoustical
performance.
E. Cap open ends of attenuators at factory with plastic, heavy duty paper, cardboard, or other
appropriate material to prevent entrance of dirt, water, or any other foreign matter to inside of
attenuator. Caps shall not be removed until attenuator is installed in duct system.
2.12 PREFABRICATED ROOF CURBS
Galvanized steel or extruded aluminum 300 mm (12 inches) above finish roof service, continuous
welded corner seams, treated wood nailer, 40 mm (1-1/2 inch) thick, 48 kg/cubic meter (3
pound/cubic feet) density rigid mineral fiberboard insulation with metal liner, built-in cant strip
(except for gypsum or tectum decks). For surface insulated roof deck, provide raised cant strip
(recessed mounting flange) to start at the upper surface of the insulation. Curbs shall be
constructed for pitched roof or ridge mounting as required to keep top of curb level.
2.13 FIRESTOPPING MATERIAL
Refer to Section 07 84 00, FIRESTOPPING.
2.14 SEISMIC RESTRAINT FOR DUCTWORK
Refer to Section 13 05 41, SEISMIC RESTRAINT REQUIREMENTS FOR NON-STRUCTURAL
COMPONENTS.
2.15 DUCT MOUNTEDTEMPERATURE SENSOR (AIR)
Refer to Section 23 09 23, DIRECT-DIGITAL CONTROL SYSTEM FOR HVAC.
2.16 INSTRUMENT TEST FITTINGS
A. Manufactured type with a minimum 50 mm (two inch) length for insulated duct, and a minimum 25
mm (one inch) length for duct not insulated. Test hole shall have a flat gasket for rectangular
ducts and a concave gasket for round ducts at the base, and a screw cap to prevent air leakage.
B. Provide instrument test holes at each duct or casing mounted temperature sensor or transmitter,
and at entering and leaving side of each heating coil, cooling coil, and heat recovery unit.
2.17 AIR FLOW CONTROL VALVES (AFCV)
Refer to Section 23 36 00 / 23 82 00, AIR TERMINAL UNITS / CONVECTION HEATING and
COOLING UNITS.
2.18 LEAD COVERED DUCT
A. Sheet Lead: 3.1 mm (1/8 inch) thick, securely installed, free of waves, lumps or wrinkles and with
as few joints as possible.
B. Joints shall be made to obtain X-ray absorption equivalent to adjacent sheet lead, and finished
smooth and neat.
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2.19 ELECTROSTATIC SHIELDING
A. At the point of penetration of shielded rooms ducts shall be made electrically discontinuous by
means of a flexible, nonconductive connection outside shielded room.
B. Metallic duct portion inside shielded room shall be electrically bonded to shielding.
PART 3 - EXECUTION
3.1 INSTALLATION
A. Comply with provisions of Section 23 05 11, COMMON WORK RESULTS FOR HVAC and
STEAM GENERATION, particularly regarding coordination with other trades and work in existing
buildings.
B. Fabricate and install ductwork and accessories in accordance with referenced SMACNA
Standards:
1. Drawings show the general layout of ductwork and accessories but do not show all required
fittings and offsets that may be necessary to connect ducts to equipment, boxes, diffusers,
grilles, etc., and to coordinate with other trades. Fabricate ductwork based on field
measurements. Provide all necessary fittings and offsets at no additional cost to the
government. Coordinate with other trades for space available and relative location of HVAC
equipment and accessories on ceiling grid. Duct sizes on the drawings are inside dimensions
which shall be altered by Contractor to other dimensions with the same air handling
characteristics where necessary to avoid interferences and clearance difficulties.
2. Provide duct transitions, offsets and connections to dampers, coils, and other equipment in
accordance with SMACNA Standards, Section II. Provide streamliner, when an obstruction
cannot be avoided and must be taken in by a duct. Repair galvanized areas with galvanizing
repair compound.
3. Provide bolted construction and tie-rod reinforcement in accordance with SMACNA
Standards.
4. Construct casings, eliminators, and pipe penetrations in accordance with SMACNA
Standards, Chapter 6. Design casing access doors to swing against air pressure so that
pressure helps to maintain a tight seal.
C. Install duct hangers and supports in accordance with SMACNA Standards, Chapter 4.
D. Install fire dampers, smoke dampers and combination fire/smoke dampers in accordance with the
manufacturer's instructions to conform to the installation used for the rating test. Install fire
dampers, smoke dampers and combination fire/smoke dampers at locations indicated and where
ducts penetrate fire rated and/or smoke rated walls, shafts and where required by the Resident
Engineer. Install with required perimeter mounting angles, sleeves, breakaway duct connections,
corrosion resistant springs, bearings, bushings and hinges per UL and NFPA. Demonstrate
re-setting of fire dampers and operation of smoke dampers to the Resident Engineer.
E. Seal openings around duct penetrations of floors and fire rated partitions with fire stop material as
required by NFPA 90A.
F. Flexible duct installation: Refer to SMACNA Standards, Chapter 3. Ducts shall be continuous,
single pieces not over 1.5 m (5 feet) long (NFPA 90A), as straight and short as feasible,
adequately supported. Centerline radius of bends shall be not less than two duct diameters. Make
connections with clamps as recommended by SMACNA. Clamp per SMACNA with one clamp on
the core duct and one on the insulation jacket. Flexible ducts shall not penetrate floors, or any
chase or partition designated as a fire or smoke barrier, including corridor partitions fire rated one
hour or two hour. Support ducts SMACNA Standards.
G. Where diffusers, registers and grilles cannot be installed to avoid seeing inside the duct, paint the
inside of the duct with flat black paint to reduce visibility.
H. Control Damper Installation:
1. Provide necessary blank-off plates required to install dampers that are smaller than duct size.
Provide necessary transitions required to install dampers larger than duct size.
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2. Assemble multiple sections dampers with required interconnecting linkage and extend
required number of shafts through duct for external mounting of damper motors.
3. Provide necessary sheet metal baffle plates to eliminate stratification and provide air volumes
specified. Locate baffles by experimentation, and affix and seal permanently in place, only
after stratification problem has been eliminated.
4. Install all damper control/adjustment devices on stand-offs to allow complete coverage of
insulation.
I.
Air Flow Measuring Devices (AFMD): Install units with minimum straight run distances, upstream
and downstream as recommended by the manufacturer.
J.
Low Pressure Duct Liner: Install in accordance with SMACNA, Duct Liner Application Standard.
K. Protection and Cleaning: Adequately protect equipment and materials against physical damage.
Place equipment in first class operating condition, or return to source of supply for repair or
replacement, as determined by Resident Engineer. Protect equipment and ducts during
construction against entry of foreign matter to the inside and clean both inside and outside before
operation and painting. When new ducts are connected to existing ductwork, clean both new and
existing ductwork by mopping and vacuum cleaning inside and outside before operation.
3.2 DUCT LEAKAGE TESTS AND REPAIR
A. Ductwork leakage testing shall be performed by the Testing and Balancing Contractor directly
contracted by the General Contractor and independent of the Sheet Metal Contractor.
B. Ductwork leakage testing shall be performed for the entire air distribution system (including all
supply, return, exhaust and relief ductwork), section by section, including fans, coils and filter
sections. Based upon satisfactory initial duct leakage test results, the scope of the testing may be
reduced by the Resident Engineer on ductwork constructed to the 500 Pa (2" WG) duct pressure
classification. In no case shall the leakage testing of ductwork constructed above the 500 Pa (2"
WG) duct pressure classification or ductwork located in shafts or other inaccessible areas be
eliminated.
C. Test procedure, apparatus and report shall conform to SMACNA Leakage Test manual. The
maximum leakage rate allowed is 4 percent of the design air flow rate.
D. All ductwork shall be leak tested first before enclosed in a shaft or covered in other inaccessible
areas.
E. All tests shall be performed in the presence of the Resident Engineer and the Test and Balance
agency. The Test and Balance agency shall measure and record duct leakage and report to the
Resident Engineer and identify leakage source with excessive leakage.
F. If any portion of the duct system tested fails to meet the permissible leakage level, the Contractor
shall rectify sealing of ductwork to bring it into compliance and shall retest it until acceptable
leakage is demonstrated to the Resident Engineer.
G. All tests and necessary repairs shall be completed prior to insulation or concealment of ductwork.
H. Make sure all openings used for testing flow and temperatures by TAB Contractor are sealed
properly.
3.3 TESTING, ADJUSTING AND BALANCING (TAB)
Refer to Section 23 05 93, TESTING, ADJUSTING, and BALANCING FOR HVAC.
3.4 OPERATING AND PERFORMANCE TESTS
Refer to Section 23 05 11, COMMON WORK RESULTS FOR HVAC and STEAM GENERATION
END OF SECTION 23 31 00
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